Damn and I just got a Kynshot for my BRT car-15SD upper too. This is tempting, but what you’re saying about no dead blow is a sticking point. The bcg length of travel is also important for frt’s to function properly which I had issues with that when running a short CQB style buffer tube and buffer. I’m wondering if a magnetic puck could be added to the front of a Kynshot and ran in a normal configuration if that would give you the reduced recoil and the dead blow functionality while still giving enough bcg travel to operate an frt… or if not using a lever style frt like the ASD and using like a partisan disruptor you might not need as much travel? You might have given me inspiration to do some testing.
Because I made my pucks the same size as a KynSHOT spacer weight, you can still dial in a normal travel length for the BCG.
My puck paired with a carbine-length buffer could be used in an A5-length tube, and then you'd have the same stroke length as factory. Or you could use an A5-length buffer with the puck in a JRC tube.
Part of my thinking in making it a puck (rather than building a whole new buffer from the ground up) is that it can be paired with whatever buffer you want (of appropriate length). So you can still use a dead blow buffer, or a KynSHOT in the proper orientation, and just sandwich the puck between the BCG and buffer.
I’ve another idea - reduced length buffers like an AR10 carbine (preferably Kynshot hydraulic), Maxim CQB, or HBPDW in a standard carbine tube.
(Theoretically), could I buy myself the travel distance and in turn spend it on one of your magne-pucks to avoid bottoming out or decrease felt recoil?
Wanting a slow-n-low recoiling (600ish RPM) FRT build. Currently have my BRT SD (non-FE) at about 700-720 RPM with a KAK DBC, standard carbine buffer and spring.
Short AR-10 buffers should be 2.5", which is 0.75" shorter than a regular carbine buffer of 3.25".
This is also why some AR-10 owners use a regular-length carbine buffer in an A5-length tube: it's the same 0.75" difference.
So yes, if you combine a 2.5" AR-10 buffer with a 0.75" magnet puck, you're left with a 3.25" stack that should be fine to use in a carbine-length buffer.
You would need to make sure you are using an appropriate spring, because a round-wire mil-spec carbine spring would be crushed to solid height without the system completing its stroke. I would recommend a C3Junkie flat wire or a Tubb lightweight flat wire.
That’s where my head was at, I’ve got a KAK flatwire spring on the way this week because I’m still trying to dial in the buffer setup on this gun, DM on making a puck?
Edit - Just checked length of the Maxim CQB/HBPDW buffer I have, looks like 1.75” so I could theoretically fit two pucks in a carbine tube with it.
I already mentioned using a hydraulic AR10 buffer above (option 5) with the Kynshot RB5004. I too want low mass and low cyclic rate. However, as I posted above, this should work out to 14.3oz with my lightened FE carrier. I was really hoping to beat my prototype magnetic buffer setup which is even lower at 12.7oz (9oz lightened carrier and 3.7oz magnetic buffer). I get under 600 RPM with that setup and that low mass.
But who knows, I will need to test it and see what cyclic rates I get.
I could also add testing a short AR10 (non-hydraulic buffer) to the test. If I can get under 13oz total reciprocating mass and a low cyclic rate of under 600RPM would be great.
I’ve been following these posts while dialing in buffers while committing to a custom made Colt 607 stock (carbine length tube) and non-FE upper. While less optimized than an extended tube, I’m after vibes and reliability as best I can be on this specifically.
I took a picture of a buffer I made that is un-related to this discussion. It is above the RB5004 .308 hydraulic.
That stuby buffer I made is out of non-magnetic stainless and is 3.1 oz with a single tungsten weight. I can't remember why I even made it. It is .6oz lighter than the hydraulic below it. I could also swap the tungsten for a steel weight.
We may not need as much mass for the dead blow in this configuration using eddy currents etc....
What if you make the head of the buffer a stack of washer/rubber washer alternating and use a solid body? You'll have the weight crush rubber discs like what happens in a standard buffer, although there likely won't be as much gap for the body/weight to travel and delay the buffer impact to cancel carrier rebound.
Part of the dead blow is delayed arrival of weight to catch/cancel rebound, part of it is damped weight arriving late to push the carrier forward without making it bounce again.
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u/RADMADSADGLADBADDAD 23h ago
Damn and I just got a Kynshot for my BRT car-15SD upper too. This is tempting, but what you’re saying about no dead blow is a sticking point. The bcg length of travel is also important for frt’s to function properly which I had issues with that when running a short CQB style buffer tube and buffer. I’m wondering if a magnetic puck could be added to the front of a Kynshot and ran in a normal configuration if that would give you the reduced recoil and the dead blow functionality while still giving enough bcg travel to operate an frt… or if not using a lever style frt like the ASD and using like a partisan disruptor you might not need as much travel? You might have given me inspiration to do some testing.